This is the name given to european countries during the cold war who were allied with the soviet union and its mutual defense organization, the warsaw pact.
Cold War alliances like NATO and the Warsaw Pact both reflected and intensified the divisions between democratic and socialist nations. In the years following World War II, European nations took steps to align with others to protect themselves from future aggression. Some expected this might come from resurgent Nazism, either as a secret counter-attack or as guerrilla resistance to Allied occupation. Others believed the menace would come from Soviet aggression. In March 1947, Britain and France signed the Treaty of Dunkirk, a bipartisan military alliance. In March 1948 they extended this alliance by signing the Treaty of Brussels, a new agreement that included Belgium, Luxembourg and the Netherlands. Though the Treaty of Brussels did not specifically mention the Soviet Union, it was predicated on resisting communism and communist expansion. The treaty’s preamble made its political aims quite clear: to “fortify and preserve the principles of democracy, personal freedom and political liberty, the constitutional traditions and the rule of law” that were the “common heritage” of the five signatory nations.